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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 28 December 2016 by Guest Author

Exceptionally high temperatures across the Arctic this winter are unprecedented in the modern record, and extremely unlikely to occur were it not for the influence of greenhouse gases, according to new research.

A “heatwave” in mid-November caused some parts of the Arctic to be 15C warmer than usual, with average temperatures for November and December across the Arctic as a whole a full 5C above the long term average, according to the quickfire analysis of this year’s unusual winter.

Such an extremely warm winter in Earth’s northern extremity is still a rare event but climate change has “made the event more likely by orders of magnitude”, the authors tell Carbon Brief.

If climate change continues unchecked, we could see similarly high temperatures in the Arctic every other year by the second half of this century, today’s analysis suggests.

November-December temperature anomalies showing some Arctic regions up to 10C warmer than usual for this time of year. Source: World Weather Attribution.

The work, carried out by the World Weather Attribution (WWA) project, is the latest in what are known as “single event attribution” studies. Other recent studies by the same group found that climate change made torrential rains unleashed on south Louisiana in Augusttwice as likely.

‘Unprecedented’ warmth

The Arctic is the fastest warming place on Earth. Temperatures are rising 2.5 times faster than the Earth as a whole, the analysis explains. Warming is most notable in winter, with satellite estimates of November-December temperatures at the North Pole showing a clear upward trend since 1990.

Temperature measurements taken at ground level further south in the Arctic stretch back much further, to around 1900. At 5C above the 1951-1980 average, Arctic temperatures in November-December 2016 are “unprecedented” in the modern record, say the authors of today’s research.

Nov-Dec temperature anomalies relative to 1951–1980 in the Arctic averaged over 70–80N. Green line is the 10-year running average. Source: World Weather Attribution.

The high temperatures have had serious implications for the freezing up of sea ice that usually happens at this time of year. The area of sea ice covering the Arctic ocean even stopped growing and started shrinking in the Barents Sea for a brief period in November. You can read more here about how the last few months have capped off an exceptional year for the Arctic.

Human influence

Did human-caused climate change alter the chances of record high temperatures in the Arctic this winter? To answer this question, the scientists compared actual measurements for the Arctic in November and December with two different “versions” of 13 different climate models.

One combined scientists’ best understanding of how natural variability and greenhouse gases drive temperatures changes in the Arctic. The other replicated a hypothetical world where natural variability exists but there is no long-term warming coming from greenhouse gases.

The results suggest that an event like 2016, or a hotter one, would have been “extremely unlikely” without human-induced climate change. In a world with just natural influences, such an event wouldn’t have happened at all, the authors say.

The scientists got a very similar result when they repeated their analysis with a different set of models (those used in the Weather@Home project), strengthening confidence in their conclusion that the record high temperatures were highly unlikely in the absence of climate change.

Dr Geert Jan van Oldenborgh from The Royal Netherlands Meteorological Institute (KNMI), one of the team of scientists who carried out the work, tells Carbon Brief why using multiple methods is important, particularly somewhere as remote as the Arctic. He says:

“Observations in that part of the world are rare… by combining independent methodologies we are able to assess what we can say independent of a specific uncertain methodology.”

While previous years have also seen large spikes in November-December temperatures, these peaks are occurring on top of a upward trend, says Prof Jennifer Francis, an expert in Arctic climate change at Rutgers University. She tells Carbon Brief:

“The far north has indeed been behaving bizarrely in Nov/Dec 2016, setting many new records for temperature, sea ice extent, atmospheric water vapour content, and Arctic amplification (the difference in temperature between the Arctic and northern mid-latitudes)”

The “uptick” in Arctic amplification is most worrisome, says Francis, because of the possible implications for extreme weather much further south. She tells Carbon Brief:

“Recent studies by several groups suggest that a very warm Arctic in late fall – particularly in the region north of Scandinavia as we’ve seen this year – tends to favour cold spells in Eurasia…This year’s records portend a very “interesting” winter for the northern hemisphere.”

‘Commonplace’

The scientists behind today’s analysis used the same 13 climate models to investigate how often we might see a repeat of such high Arctic winter temperatures in future as warming continues.

They found that by about 2050, extreme heat like the Arctic experienced in 2016 will be “commonplace” if emissions continue unchecked, with around half of Arctic winters as hot or hotter. Or as Dr Friederike Otto, an expert in modelling extreme events at the University of Oxford and part of the research team, tells Carbon Brief:

“If nothing is done to decrease greenhouse gas emissions a rare event like this could be expected to happen every other year by the second half of this century.”

Even if global temperature rise was halted at 2C above pre-industrial levels – the internationally agreed target – temperatures as high as those in 2016 would not be considered unusual, say the scientists. This should be cause for great concern, Otto adds:

“The Arctic is warming faster than any other region on Earth and is changing beyond recognition as open water replaces sea ice and permafrost is thawing. It is one of the large ecosystems where we already see a large impact of anthropogenic climate change.”

Arctic sea ice extent for 2016, up to and including 20 December. Source: NSIDC.

Though the results from attribution studies such as this one tend to be released before they’ve been through the traditional process of peer-review, the methods underpinning them are peer-reviewed and well established, van Oldenborgh tells Carbon Brief. And the methods scientists use to assessing the human contribution to extreme events are advancing all the time, he adds:

“As a region with not many observations and unique modelling challenges, it is a different challenge than e.g. in [the] Louisiana [floods]…We are constantly learning.”

With changes in the Arctic so pronounced this year, it’s important that attribution efforts are channelled into these high latitude regions. As Dr Mark Serreze from the US National Snow and Ice Data Set (NSIDC), who wasn’t involved in the new analysis, explains to Carbon Brief:

“I am always cautious about reading too much into individual extreme events. However, what has happened in the Arctic last winter and this autumn has certainly caught my attention.”

Comments

The arctic warmth in recent decades is being driven partly by a positive feedback from declining ice cover exposing more ocean, so this warmth would tend to stay near the surface for some time. Could this partly explain why the surface as measured by Giss is heating a little more rapidly than the middle of the atmosphere in the UAH data?

Some commenter here (sorry I forgot who & cannot find) suggested the years following extreme ElNino recorded very large summer ice extent minima (e.g. 2007, 2012) whereas the next years featured the"recovery" to the long-term trend. The commenter speculated if there is any mechanism responsible for such delayed influence of ElNino in the arctic so that the season of the relatively largest melt is likely tobe the following season, but no one came up with anything.

The topic is interesting and the speculation appears to be confirmed by this year's poor freezing season (past record 2015-16 ElNino) but it remains to be seen what the melting season of Northern autumn 2017 will bring.

To a large extent, statistical analysis and prediction of the likely frequency of various events depends on past records and that inputs are the same now, on average, as they have ever been. In this completely new scenario of Carbon dioxide above 400ppm and climbing, all bets are off. The now famous tipping points are likely to be sending the climate into new territory that past experience can not predict.

chrickoz@2,I made comments about minimum Arctic Sea Ice extents occuring in the years following an El Nino event. Looking at El Nino events based on the ONI presentation by NOAA there appears to be a related pattern in the minimum summer Arctic Sea Ice extents presented by NSIDC in the Charctic Interactive Sea Ice Graph. The minimum sea ice extent appears to be significantly below the trend line of Arctic Minimum one or two years after an El Nino event.

Based on my crude evaluation of the magnitude and duration of the ONI values for the different events the most significant (H) ONI value events since near the 1979 beginning of the NSIDC presentation were: 1982/83, 1997/98 and 2014/15/16. The next group of moderately significant (M) ONI value events were: 1986/87/88, 1991/92, 2002/3, 2009/10. And the last group of least significant (L) ONI value events were: 1976/77, 1977/78, 1979/80, 1994/95, 2004/5, and 2006/7.

A good presentation of the relevant data would be to superimpose the Arctic Sea Ice Extent graph (the one from NASA) on an inverted presentation of Jan Null's ONI graph (inverted so that El Nino is down).

But I am not skilled at creating and presenting graphs. So I offer the following presentation of the sea ice extents relative to the ONI events and their relative intensity (L, M, H) with the approximate yearly minimum Arctic Sea Ice from the NSIDC and the September Average from NASA extent in million square km as the value near inside the (Min from NSIDC - Sept form NASA; The closer the values are the flatter/broader the minimum extent was through September):

1976/77 (L)

1977/78 (L) - No NSIDC ice extents prior to 1979

1979/80 (L) - 1979 (7.0 - 7.19), 1980 (7.6-7.83)

1981 (7.0- 7.24)

1982/83 (H) - 1982 (7.2-7.44), 1983 (7.3-7.61)

1984 (6.5-7.10)

1985 (6.6-6.91)

1986/87/88 (M) - 1986 (7.2-7.53), 1987 (7.0-7.47), 1988 (7.2-7.48)

1989 (7.0-7.03)

1990 (6.1-6.23)

1991/92 (M) - 1991 (6.40-6.54), 1992 (7.3-7.54)

1993 (6.3-6.50)

1994/95 (L) - 1994 (7.0-7.18), 1995 (6.1-6.12)

1996 (7.3-7.87)

1997/98 (H) - 1997 (6.7-6.73), 1998 (6.4-6.55)

1999 (5.9-6.23)

2000 (6.1-6.31)

2001 (6.7-6.74)

2002/3 (M) - 2002 (5.7-5.95), 2003 (6.1-6.13)

2004/5 (L) - 2004 (5.9-6.04), 2005 (5.4-5.56)

2006/7 (L) - 2006 (5.9-5.91), 2007 (4.3-4.29)

2008 (4.7-4.72)

2009/10 (M) - 2009 (5.2-5.38), 2010 (4.7-4.92)

2011 (4.4-4.61)

2012 (3.4-3.62)

2013 (5.1-5.35)

2014/15/16 (H) - 2014 (5.1-5.28), 2015 (4.5-4.63), 2016 (4.2-4.72)

2017 - Yet to be seen

Low events that occur one or two years after an El Nino are:

1984 and 1985 following the 1982/83 (H) event

1990 following the 1986/87/88 (M) event

1993 following 1991/92 (M) event

1999 and 2000 following the 1997/98 (H) event

2007 and 2008 following the series of 2002/3, 2004/5, 2006/7 (L) events

2011 and 2012 following the 2009/10 (M) event

1996 is a year that clearly does not fit the pattern of low extents one or two years after an El Nino. This could be because the 1994/95 event was a very weak El Nino followed by a La Nina in 1995/96.

If a pattern similar to the years following the 2009/2010 occurs then the Arctic Sea Ice minimum in 2017 will be lower than 2016 and the minimum in 2018 could be even lower, potentially setting a new record minimum, especially if La Nina does not develop.

"A good presentation of the relevant data would be to superimpose the Arctic Sea Ice Extent graph (the one from NASA) on an inverted presentation of Jan Null's ONI graph (inverted so that El Nino is down)."

Also blew it when trying to embellish the folowing part of my comment@4. The following is a better presentation.

"I am not skilled at creating and presenting graphs. So I offer the following presentation of the sea ice extents relative to the ONI events and their relative intensity (L, M, H). I have included the approximate annual minimum the NSIDC Charctic Graph as well as the September Average from NASA. Extents are are in million square km presented following each year (Min from NSIDC Charctic - September average from the NASA graphic; The closer these values are the flatter/broader the minimum extent was through September):"

I am becoming more and more exasperated with the way scientists word their dispatches to the public.

"Record-breaking Arctic warmth ‘extremely unlikely’ without climate change" just doesn't do it ... every Tom, Dick, and Harriet will be saying - ahh - but it COULD have happened without climate change.

What John Q. Public ( Q. for Idiot) should hear is simply - this insane warmth in the Arctic could not happen without human-caused climate change! - PERIOD.

I am an engineer with an MBA. I have been thinking about issues like climate change and global economic inequity for a long time. I was a fan of things like Fair Trade far before I became aware of the climate change issue. I became aware of the climate change issue before Kyoto made the headlines because of the changes to climate design requirements of structures and surface water managment systems. And the climate changes also increase the inequities that actions like Fair Trade try to develop truly sustainable solutions to.

As an engineer I constantly seek increased awareness and improved understanding of what is going on and strive to apply that understanding to create something that will achive a desired objective without creating unacceptable future consequences others will have to deal with.

Recent global events and this holiday break has allowed me to advance or clarify my understanding.

I am becoming more certain that it would be better for everyone to be constantly hearing:

It is unacceptable for any portion of humanity to benefit from an activity that ultimately is a limited opportunity, like the burning up of buried ancient hydrocabons, or an activity that creates challenges and problems others will have to deal with, like the actions associated with the exctraction, transport, processing, and burning up of buried ancient hydrocabons.

The preface for that constant reminder message to everyone would be:

The aspiration/objective of human life is to help advance global humanity to be a part of a lasting better future for all life on this or any other amazing planet.

And the concluding reminder would be the understanding that:

'The freedom of everyone to believe what they wish and do as they please is the best way for things to be', only applies if everyone is honestly dedicated to helping to advance humanity to that lasting better future.

That set of constant reminders would annoy and disappoint some people, but they would have to admit they deserve to be annoyed and disappointed until they change their minds and become more helpful, less harmful.

And all the leaders/winnersaround the globe, and anyone aspiring to be a leader/winner, would be expected to be the ones delivering those constant reminders that annoy, disappoint and discourage those who deserve it. And any leader (wealthy, influential, in business or politics), who can be shown to fail to honestly dedicate themselves to that task of promoting awareness and better understanding of the changes required to honestly advance humanity deserves to be removed from their position of leadership, wealth or influence (until they prove that they have changed their minds and decided to become helpful rather than harmful regarding the advancement of humanity to a lasting better future for all).

There clearly are many issues deserving increased awarness and the changing of minds about developed social and economic activity and attitudes, far more than just climate change. Perhaps a 'punchier' way of referring to every instance could be to say they are one of the many fronts of the 'War for the Future of Humanity'.

Perhaps that would help everyone fighting on one of those fronts see more of a connection between their actions and all of the other fronts, like the connection between Fair Trade and Climate Change, or the connection between the design of safe structures and Climate Change.

Last year, before La Nina we heard about the N. Pacific blob of warm water (2-4C warmer than it should be) ...

Recent forecasts, where the ocean surface temperatures indicate a weak La Nina (about 0.5C cooler) ... showed on NOAA produced maps that the "blob" had moved to be just south of the Bering strait (in November 2016) ... it seems that this warm Pacific Ocean water left over from the last El Nino (?) is heading into the Arctic, reducing the amount of seawater ice and ice thickness.

KeenOn350, I totally understand your frustration. The way scientists talk in probabilities and conditionality may be fustrating, but its also the truth about various issues. We should not distort the truth. Hopefully most people can understand thats the way science does work on the basis of probabilities.

Oooooooooooo, extremely unlikely. That will really convince people to ignore those claiming reality is a myth.

Climate scientists need to up their game. EVERY statement that climate scientists make needs to open with the following:

When it comes to global warming there is no debate, there is no discussion, and there is no opinion. There are only those who want to commit mass murder on a global scale with global warming, and those who do not want to commit mass murder on a global scale.

The difference between Conservatives and ISIL/Daesh members: ISIL/Daesh members are a better class of hominid because at least they don’t lie about wanting to murder us.

Claiming that global warming is a hoax is worse than sitting around a Hamburg apartment planning to hijack passenger jets and crash them into office towers.

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Moderator Response:

[DB] As others have noted, future comments standing in direct violation of this site's Comments Policy are subject to summary deletion. At the discretion of the moderators, future posting ability may be rescinded.

Kuni @11, according to Rogelj et al's Probability Density Function (PDF) of the IPCC statements on the Equilibrium Climate Response, there is up to a 5% chance, based on all the evidence, that the temperature response from a doubling of CO2 after feedbacks will be less than that expected with no feedbacks. There is a near one in three chance that the temperature response will be 2 C or less, and a 50% chance it will be less than 2.5 C. Indeed the most likely single value (mode of the PDF) is around 1.7 C.

The IPCC do not commit to a specific PDF, and alternate PDFs consistent with their statement give different but similar values for low temperature responses. Any reasonable PDF for their statements will give a modal temperature of 2 C or less. It follows that "luke warmers", the most rational camp within the agw "skeptic" community, are not wrong to think that a low temperature response has a reasonably high probability. Where they tend to be wrong is in downplaying or rejecting the low (25% or less, depending on PDF) risk of an ECS above 3 C; generally by restricting the data they will accept. They are guilty of unreasonably high certainty, based on undully restricted evidence - ie, of dogmatism.

The IPCC uncertainty about impacts is greater than it uncertainty about ECS, with a corresponding higher probability of low impacts from significant temperature increases. Again, the expectation of such low impacts is not entirely unreasonable. What is unreasonable about the "skeptic" position is the unwarranted exclusion of the probability of high impacts. Not certainty, of, but probability of.

The upshot is that your position, which unreasonably excludes the probability of low temperature responses and low impacts is (at best) at least as dogmatic and irrational as that of the AGW "skeptics". Indeed, any position that neglects the low probability of a soft landing from AGW and expresses dogmatism that the impacts will be high if we do nothing is contrary to the science. What is the case is that the probability of such a soft landing is low, being the product of two probabilities already less than 50%. And ignoring that for rhetorical reasons merely makes us easy to ignore.

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